Determination of ammonia and urea in urine and of urea in blood by use of an ammonia-selective electrode.

I propose a single, quick method for measuring ammonia in urine and urea in plasma and urine. An ammonia-selective electrodie is used, set up on a microcell, which allows use of small sample volumes. Ammonia is measured directly after partial conversion of ammonium ions to NH3. Urea is measured after its hydrolysis by urease. With urine, the two procedures can be carried out successively in the same cell and on the same sample without changing the procedural conditions. Linear electrode response and accuracy have been checked for concentrations in the expected (normal) range.